Certain substituted s-triazolo [3,4-b]benzothiazoles (hereinafter referred to as "triazolobenzothiazole compounds") are employed for the control of plant pathogens, including fungal organisms and bacterial organisms. Thus, the triazolobenzothiazole compounds can be employed for the control of such organisms as crown gall, rice blast, leaf rust, powdery mildew, anthracnose, and the like. The compounds are particularly suited for the control of fungal organisms, and give particularly good results in the control of rice blast. Belgium Pat. No. 789,918 describes their preparation by cyclodehydration of 2-acylhydrazinobenzothiazole compounds with polyphosphoric acid.
It is a purpose of this invention to provide a novel process for the preparation of triazolobenzothiazole compounds, useful as plant fungicides, and in addition to provide new intermediate 1-acyl-4-(o-halophenyl)thiosemicarbazide compounds and 4-(o-halophenyl)-1,2,4-triazole-3-thiol compounds which are utilized in the preparation of such triazolobenzothiazole compounds.